Manufacture of paper tubes



Patented Jan. 16, 1934 to Remington Arms Company,

ration of Delaware 1110., a corpo- No Drawing. Application November 15, 1929 Serial No. 407,581

9 Claims. (01. 93-94) The present invention relates to the manufacture of articles of paper, more especially to wound paper tubes used in the manufacture of shot shells, and embodies improved methods for treating such tubes to render the same waterproof and charproof.

In the manufacture of shot shells, a tube for shell bodies is customarily formed by winding a sheet of paper about a mandrel into a tube of 10 four or more wraps of paper. A substance, such as a starch paste, is usually applied to the paper during the winding operation to cause adhesion between the wraps of the paper and to give increased rigidity to the tube. After winding, the

tubes are stripped from the mandrel, are passed through dies, either rotary or stationary, to be brought to a proper size, are dried, and are subjected to several treatments for the purpose of rendering the tubes resistant against powder burns on discharge of the shot shells and for rendering the shot shell tubes waterproof when exposed to moisture.

A treatment commonly in use consists in dipping the wound tube in molten paraifin wax to impregnate the layers of paper with paraffin in order to provide the inner layers with a charproof substance effective to block the heat of powder combustion on discharge to prevent excessive charring of the paper of the tube. Parafiin so used effectually protects the tube against powder burns but does not render it adequately waterproof. In order to effectually waterproof the shot shell tube it becomes necessary to apply a waterproofing substance. It has been found that a very desirable substance for waterproofing consists of a quickly drying spirit varnish, a pyroxylin lacquer, or a pyroxylin resin lacquer. Any such lacquer or varnish will for the purpose of this application be termed lacquer.

The problem of applying such a waterproofing lacquer to a paraffin impregnated tube is exceedingly difiicult, owing to the peculiar reaction between the parafiin wax and the solvents ordinarily used in such lacquer, setting up what appears to be a paint remover effect rendering a large portion of the lacquer soft and tacky for an in definite period and seriously hindering the forming of a hard, impervious lacquer coat. It is very desirable therefore, to eliminate the use of paraffin in shot shell manufacture and substitute a substance which does not entail the difiiculties above discussed.

In my co-pending application, Serial No. 355,458, filed April 16, 1929, I have disclosed a method of manufacturing shot shells wherein the use of parafiin is entirely eliminated and wherein the shot shell tube is charproofed by incorporating in its inner layers a lacquer plasticizer which is effective as a charproofing material and which permits the forming of an effective waterproofing coat of lacquer Varnish on the outer surface of the finished shell. The present invention also contemplates the elimination of paraffin in shot shell manufacture and further contemplates improved methods in the manufacture of tubes for shot shells to render the same waterproof and charproof.

It is an object of the. present invention to provide a shot shell having a paper tube body which is both impervious to moisture and highly resistant against powder burns.

t is a further object of the present invention to provide an improved method for manufacturing shot shells wherein the tube is waterproofed before it is loaded and crimped, thus making possible the completion of the shot shell at the loading machine without necessitating any after treatment.

It is a further object of the present invention to provide an improved shot shell having a coat of impervious lacquer on its inner wall, thereby preventing the creeping of any substance contained in the paper tube into the powder or other materials contained in the tube.

It is a further object of the present invention to provide a shot shell tube coated with a moisture impervious lacquer on its inner and outer walls and containing therebetween a charproo-fing' substance impregnated in the tube.

With these and other objects in view, the inventio-n comprises the improved methods and articles produced thereby as set forth in the following description.

The preferred method for making a waterproof and charproof shot shell according to the present invention comprises the following steps:

1. The paper tube is wound and sized according to known methods. A starch paste may be applied to the tube in winding, as is customary. In sizing it is preferred to use a stationary die rather than a rotary die, because the former is found to leave the fibres of the paper tube in a less compactly compressed state than when a rotary die is used; this being desirable to give a surface to which a lacquer may more easily adhere and which affords easier penetration. Further, with the use of a stationary die no lubricant is necessasry.

2. The sized tube is immersed in a heated bath of an impregnating substance which is a lacquer 9 plasticizer and is additionally capable of preventing charring of the paper of the tube on firing of the shot shell. Castor oil qualifies as such a substance although other substances may be used, as will be pointed out hereinafter. After removal from this bath the tube is permitted to stand for a sufficient time to permit the impregnating substance to penetrate into and fill the interstices of the paper.

The impregnated tube is then dipped into a solution comprising as constituents a lacquer base, such for example as a nitrocellulose such as low-viscosity pyroxylin, and a suitable volatile solvent such as acetone. It is to be noted that this solution into which the impregnated tube is dipped comprises a lacquer base and a solvent but lacks a plasticizing ingredient, the plasticizer being furnished from that already in the tube. It is found that the proper quantity of plasticizer is taken from the tube and is diffused throughout the lacquer film, which is formed from the dipping, to make a coating which is hard on its surface, which is tough and flexible and which is securely bonded with the paper of the tube. Although the lacquer coating thus formed is but a few thousandths of an inch in thickness, the thorough miscibility of the lacquer and plasticizer causes a partial penetration of the plasticized lacquer into the paper of the tube thereby then cut, headed and primed in the usual manher, and is now ready for loading and crimping.

5. The lacquered shell is then placed on the loading machine and is there loaded and crimped,

, the lacquer coat being sufiiciently flexible and a tough to withstand the bending of the paper in crimping without showing any sign of cracking or other injury.

6. While the shot shell is yet on the loading machine the crimp is waterproofed by dropping a v small quantity of a suitable waterproofing substance such as a quickly drying lacquer into the crimp which portion of the shell is uppermost after crimping. Or, if desired, the crimp may be waterproofed in a manner disclosed in the patent to Willis et al, No. 1,701,868, February 12, 1929, or any other suitable manner.

In the above description of the improved method, although certain ingredients are set forth as being admirably suited in producing a waterproof and charproof shot shell by my improved method, other ingredients may be used with equivalent success. Instead of castor oil, other impregnating substances such as triphenyl phos- K phate or butyl stearate which qualify as charpreventing lacquer plasticizers may be used. If

desired, the lacquer may comprise as basic constituents natural or synthetic gums or resins used alone or with nitrocellulose, it being necessary I, however to choose proper solvents and/or diluscribed. As various materials and ingredients may be used with equivalent success I do not wish to be limited to the exact materialsand ingredients which are described above for purposes of illustration, except as defined in the appended claims.

The tube of the shot shell produced by the method herein described is seen to be lacquered on its inner and outer walls, a quantity of charpreventing lacquer plasticizer being held in the paper of the tube between the two lacquer coats. The impregnating substance is thus prevented from creeping into the powder or other substance of the shot shell. The provision of a hard lacquer coat on the interior of the shot shell tube prevents the shot of the shell from embedding itself deeply into the paper of the tube with a conse quent tendency to improve shot patterns. By finishing the steps of the method at the loading machine no after treatments are necessary, and thus undesirable handling of the heavily loaded shell in hoppers and feeding devices is eliminated, together with consequent danger of injury to the finished shells which might result from such handling.

It will be understood that various changes may be made without departing from the invention as set forth in the following claims.

I claim:

1. The method of rendering a paper shot shell tube waterproof and charproof comprising impregnating the tube with castor oil and dipping the impregnated tube in a solution comprising nitrocellulose and acetone.

2. The method of rendering a paper shot shell tube waterproof and charproof comprising impregnating the tube with castor oil and dipping the impregnated tube in a solution comprising a lacquer base and a solvent.

3. The method of rendering a paper shot shell tube waterproof and charproof comprising impregnating the tube stock and surface with a char-preventing lacquer plasticizer and dippingthe impregnated tube in a solution comprising a lacquer base and a solvent, whereby a complete lacquer is formed on the tube surface.

4. The method of rendering a paper shot shell tube waterproof and charproof comprising impregnating the tube stock and surface with a char-preventing lacquer plasticizer and dipping the'impregnated tube in a solution comprising nitrocellulose and acetone, whereby a complete nitrocellulose lacquer is formed on the tube surface.

5. A paper tube for shot shells impregnated with castor oil and coated on its inner and outer walls with a nitrocellulose lacquer.

6. A paper tube for shot shells impregnated with castor oil and coated on its inner and outer walls with a waterproofing lacquer.

'7. A paper tube for shot shells impregnated with a char-preventing substance and coated on its inner wall with a lacquer to prevent creeping of said substance into the contents of the tube.

8. A paper tube for shot shells impregnated with castor oil and coated on its inner wall with a lacquer to prevent creeping of said castor oil into the contents of the tube.

9. The method of rendering a paper shot shell tube waterproof and charproof which comprises first immersing the tube in a solution having char preventing and lacquer plasticizing properties, and subsequently dipping the tube in a solution comprising a lacquer base and a solvent, whereby a complete lacquer is formed on the tube surface.

WATSON H. WOODFORD. 

